The present invention pertains to antennas, and in particular, to patch antennas, and more particularly to patch antennas and methods of assembly and fabrication of patch antennas.
Patch antennas are used in a variety of applications and are particularly useful on aircraft and guided projectiles where size, space and weight are important considerations. One problem with patch antennas is that to reduce aperture size, apertures carriers with greater permittivity have been conventionally used. This conventional approach may result in higher material costs, limitations on conformality and decreased bandwidth. The use of greater permittivity aperture carriers may require larger apertures with higher resonant frequencies. This conventional approach may also result in increased RF performance error requiring extensive band tuning. Some conventional patch antennas use multiple printed circuit boards, which require numerous piece parts and excessive touch labor for assembly, tuning and testing. These conventional patch antennas result in high cost and generally provide marginal performance.
Thus there is a general need for an improved patch antenna and improved method of fabrication and assembly of a conformal patch antenna. There is also a need for a conformal patch antenna and method of fabrication and assembly that may result in reduced assembly time, piece-part reduction, and a reduction in touch labor. There is also a need for a conformal patch antenna and method of fabrication and assembly with significantly reduced cost. There is also a need for a conformal patch antenna with improved bandwidth over conventional patch antennas. There is also a need for a conformal patch antenna with a flatter band response, which may be desirable for applications performing adaptive nulling and which may help eliminate tuning. There is also a need for a conformal patch antenna that permits a higher permittivity aperture carrier without an increase in aperture size or increase in resonant frequency. There is also a need for a conformal patch antenna suitable for acquisition of GPS signals that may be gun hardened. There is also a need for a conformal, low-cost, low-permittivity, broadband and compact patch antenna and method of fabricating such an antenna.
In accordance with embodiments of the present invention, a patch antenna comprises an aperture layer having an at least partially metallized surface. The aperture layer may have at least one aperture slot therein. The patch antenna also comprises a feed-network layer positioned adjacent to the aperture layer with a feed network metallized thereon. The aperture layer and feed-network layer may be comprised of a dielectric material having a low permittivity. The dielectric material of the aperture layer and the dielectric material of the feed-network layer may be formed in a predetermined shape by a molding process prior to metallization. The predetermined shape may, for example, be flat, or be a complex surface such as a portion of a conical, cylindrical or spherical surface. The feed network may be located within a recessed area of the feed-network layer. The feed-network layer may include at least one signal probe molded in the dielectric material and may have metallization thereon. The signal probes may also align with holes in aperture layer. An adhesive layer, ultrasonic staking/welding, or bonding method may be used to adhere the aperture layer to the feed-network layer. In one embodiment, the at least partially metallized surface of the aperture layer has up to four or more V-shaped slots circumferentially arranged therein.
In accordance with another embodiment of the present invention, an antenna system for receiving signals is provided. In this embodiment, the system includes an array of conformal patch antennas, and a combining element to combine RF signals received by the patch antennas. Each conformal patch antenna may be comprised of an aperture layer having an at least partially metallized surface that may have at least one aperture slot therein, and a feed-network layer positioned adjacent to the aperture layer and having a feed network metallized thereon. The feed network of each of the patch antennas may combine the signal components received through the aperture layer in a combining junction and provide the signals to the combining element. In this embodiment, each of the conformal patch antennas may have a substantially conical surface. The partially metallized surface of the aperture layers may have four V-shaped slots therein to form an aperture for receipt of the signals. The feed network may include circuitry to phase shift signals received approximately ninety degrees with respect to signals received through adjacent probes prior to combining by the feed network. The feed network may be designed to receive any RF signals, including circularly polarized signals and circularly polarized GPS signals. In one embodiment, the array of conformal patch antennas may be located beneath a substantially conical shaped radome such that the substantially conical surfaces of the aperture layers of the patch antennas at least in part conform to an inside surface of the radome. In this embodiment, the antenna system may be part of a guided projectile and the combined signal may be provided to a guidance system of the projectile for guidance to target coordinates utilizing GPS signals received by the patch antennas.
In yet other embodiments, the present invention provides a method of making a conformal patch antenna. The method may comprise generating a pre-shaped dielectric portion of an aperture layer and a feed-network layer, applying metallization to at least a portion of a surface of the dielectric portion of the aperture layer, and applying metallization to a recessed area of the dielectric portion of the feed-network layer. The method may also comprise providing a feed network in the metallization of the feed-network layer, providing at least one slot in the metallization on one of the surfaces of the aperture layer, and joining the aperture layer and feed-network layers to form the antenna. In one embodiment, generating the pre-shaped dielectric portions comprises molding dielectric material into either a portion of a conical, cylindrical or spherical surface to separately generate the dielectric portions of the aperture layer and feed-network layer. The method may also include joining the aperture layer and the feed-network layer with an adhesive or using an ultrasonic bonding/staking process.